Pathological role of hypoxia in Alzheimer's disease

Echocardiographic measures of the left heart and cerebrospinal fluid biomarkers of Alzheimer's disease pathology in cognitively intact adults: The CABLE study

INTRODUCTION

This study delineated the interrelationships between subclinical alterations in the left heart, cerebrospinal fluid (CSF), Alzheimer's disease (AD) biomarkers, and cognition.

METHODS

Multiple linear regressions were conducted in 1244 cognitively normal participants (mean age = 65.5; 43% female) who underwent echocardiography (left atrial [LA] and left ventricular [LV] morphologic or functional parameters) and CSF AD biomarkers measurements. Mediating effects of AD pathologies were examined. Differences in cardiac parameters across ATN categories were tested using analysis of variance (ANOVA) and logistic regressions.

RESULTS

LA or LV enlargement (characterized by increased diameters and volumes) and LV hypertrophy (increased interventricular septal or posterior wall thickness and ventricular mass) were associated with higher CSF phosphorylated (p)-tau and total (t)-tau levels, and poorer cognition. Tau pathologies mediated the heart-cognition relationships. Cardiac parameters were higher in stage 2 and suspected non-Alzheimer's pathology groups than controls.

DISCUSSION

These findings suggested close associations of subclinical cardiac changes with tau pathologies and cognition.

HIGHLIGHTS

Various subclinical alterations in the left heart related to poorer cognition. Subclinical cardiac changes related to tau pathologies in cognitively normal adults. Tau pathologies mediated the heart-cognition relationships. Subclinical cardiac changes related to the AD continuum, especially to stage 2. The accumulation of cardiac alterations magnified their damage to the brain.

The Role of Oxygen Homeostasis and the HIF-1 Factor in the Development of Neurodegeneration

Understanding the molecular underpinnings of neurodegeneration processes is a pressing challenge for medicine and neurobiology. Alzheimer's disease (AD) and Parkinson's disease (PD) represent the most prevalent forms of neurodegeneration. To date, a substantial body of experimental evidence has strongly implicated hypoxia in the pathogenesis of numerous neurological disorders, including AD, PD, and other age-related neurodegenerative conditions. Hypoxia-inducible factor (HIF) is a transcription factor that triggers a cell survival program in conditions of oxygen deprivation. The involvement of HIF-1α in neurodegenerative processes presents a complex and sometimes contradictory picture. This review aims to elucidate the current understanding of the interplay between hypoxia and the development of AD and PD, assess the involvement of HIF-1 in their pathogenesis, and summarize promising therapeutic approaches centered on modulating the activity of the HIF-1 complex.

Understanding the mechanisms of disease modifying effects of aerobic exercise in people with Alzheimer's disease

Alzheimer's disease (AD) is a very disabling disease. Pathologically, it is characterized by the presence of amyloid plaques and neurofibrillary tangles in the brain that results in neurodegeneration. Its clinical manifestations include progressive memory impairment, language decline and difficulty in carrying out activities of daily living (ADL). The disease is managed using interventions such as pharmacological interventions and aerobic exercise. Use of aerobic exercise has shown some promises in reducing the risk of developing AD, and improving cognitive function and the ability to carry out both basic and instrumental ADL. Although, the mechanisms through which aerobic exercise improves AD are poorly understood, improvement in vascular function, brain glucose metabolism and cardiorespiratory fitness, increase in antioxidant capacity and haemoglobin level, amelioration of immune-related and inflammatory responses, modulation of concentration of circulating Neurotrophins and peptides and decrease in concentration of tau protein and cortisol level among others seem to be the possible mechanisms. Therefore, understanding these mechanisms is important to help characterize the dose and the nature of the aerobic exercise to be given. In addition, they may also help in finding ways to optimize other interventions such as the pharmacological interventions. However, more quality studies are needed to verify the mechanisms.

Low HALP (Hemoglobin, Albumin, Lymphocyte, and Platelet) Score Increases the Risk of Post-Stroke Cognitive Impairment: A Multicenter Cohort Study

Objective

The HALP (hemoglobin, albumin, lymphocyte, and platelet) score is a novel indicator that measures systemic inflammation and nutritional status that has not been correlated with the risk of post-stroke cognitive impairment in patients with acute ischemic stroke or transient ischemic attack (TIA).

Methods

Study participants were recruited from 40 stroke centers in China. The HALP score was derived using a weighted sum of hemoglobin, albumin, lymphocytes and platelets, and study participants were categorized into 4 groups of equal sizes based on quartiles cutoffs of the HALP score. The Montreal Cognitive Assessment (MoCA)-Beijing Cognitive Assessment Scale (MoCA-Beijing) was performed at 2 weeks and 12 months following stroke onset. Post-stroke cognitive impairment was considered in patients with MoCA-Beijing≤22. Multiple logistic regression methods were employed to evaluate the relationship between the HALP score and the subsequent risk of developing post-stroke cognitive impairment.

Results

The study population comprised 1022 patients (mean age 61.6±11.0 years, 73% men). The proportion of individuals with MoCA-Beijing≤22 at 2 weeks was 49.2% and 32.4% at one year. Patients in the lowest quartile of HALP score (<36.56) were observed to harbor the highest risk of post-stroke cognitive impairment at 12 months post-stroke/TIA compared to those in the highest quartile (odds ratio=1.59, 95% CI=1.07-2.37, p=0.022), and lower domain scores for executive function, naming, and attention. There were no statistically significant differences between patients in the different quartiles of HALP score and HALP score at 2 weeks post-stroke/TIA.

Conclusion

The HALP score is a simple score that could stratify the risk of post-stroke cognitive impairment in stroke/TIA patients to facilitate early diagnosis and interventions.

SARS-CoV-2 Infection to Premature Neuronal Aging and Neurodegenerative Diseases: Is there any Connection with Hypoxia?

The pandemic of coronavirus disease-2019 (COVID-19), caused by SARS-CoV-2, has become a global concern as it leads to a spectrum of mild to severe symptoms and increases death tolls around the world. Severe COVID-19 results in acute respiratory distress syndrome, hypoxia, and multi- organ dysfunction. However, the long-term effects of post-COVID-19 infection are still unknown. Based on the emerging evidence, there is a high possibility that COVID-19 infection accelerates premature neuronal aging and increases the risk of age-related neurodegenerative diseases in mild to severely infected patients during the post-COVID period. Several studies correlate COVID-19 infection with neuronal effects, though the mechanism through which they contribute to the aggravation of neuroinflammation and neurodegeneration is still under investigation. SARS-CoV-2 predominantly targets pulmonary tissues and interferes with gas exchange, leading to systemic hypoxia. The neurons in the brain require a constant supply of oxygen for their proper functioning, suggesting that they are more vulnerable to any alteration in oxygen saturation level that results in neuronal injury with or without neuroinflammation. We hypothesize that hypoxia is one of the major clinical manifestations of severe SARS-CoV-2 infection; it directly or indirectly contributes to premature neuronal aging, neuroinflammation, and neurodegeneration by altering the expression of various genes responsible for the survival of the cells. This review focuses on the interplay between COVID-19 infection, hypoxia, premature neuronal aging, and neurodegenerative diseases and provides a novel insight into the molecular mechanisms of neurodegeneration.

The link between impaired oxygen supply and cognitive decline in peripheral artery disease

Although peripheral artery disease (PAD) primarily affects large arteries outside the brain, PAD is also associated with elevated cerebral vulnerabilities, including greater risks for brain injury (such as stroke), cognitive decline and dementia. In the present review, we aim to evaluate recent literature and extract information on potential mechanisms linking PAD and consequences on the brain. Furthermore, we suggest novel therapeutic avenues to mitigate cognitive decline and reduce risk of brain injury in patients with PAD. Various interventions, notably exercise, directly or indirectly improve systemic blood flow and oxygen supply and are effective strategies in patients with PAD or cognitive decline. Moreover, triggering protective cellular and systemic mechanisms by modulating inspired oxygen concentrations are emerging as potential novel treatment strategies. While several genetic and pharmacological approaches to modulate adaptations to hypoxia showed promising results in preclinical models of PAD, no clear benefits have yet been clinically demonstrated. We argue that genetic/pharmacological regulation of the involved adaptive systems remains challenging but that therapeutic variation of inspired oxygen levels (e.g., hypoxia conditioning) are promising future interventions to mitigate associated cognitive decline in patients with PAD.

Oxygen metabolism abnormality and Alzheimer's disease: An update

Oxygen metabolism abnormality plays a crucial role in the pathogenesis of Alzheimer's disease (AD) via several mechanisms, including hypoxia, oxidative stress, and mitochondrial dysfunction. Hypoxia condition usually results from living in a high-altitude habitat, cardiovascular and cerebrovascular diseases, and chronic obstructive sleep apnea. Chronic hypoxia has been identified as a significant risk factor for AD, showing an aggravation of various pathological components of AD, such as amyloid β-protein (Aβ) metabolism, tau phosphorylation, mitochondrial dysfunction, and neuroinflammation. It is known that hypoxia and excessive hyperoxia can both result in oxidative stress and mitochondrial dysfunction. Oxidative stress and mitochondrial dysfunction can increase Aβ and tau phosphorylation, and Aβ and tau proteins can lead to redox imbalance, thus forming a vicious cycle and exacerbating AD pathology. Hyperbaric oxygen therapy (HBOT) is a non-invasive intervention known for its capacity to significantly enhance cerebral oxygenation levels, which can significantly attenuate Aβ aggregation, tau phosphorylation, and neuroinflammation. However, further investigation is imperative to determine the optimal oxygen pressure, duration of exposure, and frequency of HBOT sessions. In this review, we explore the prospects of oxygen metabolism in AD, with the aim of enhancing our understanding of the underlying molecular mechanisms in AD. Current research aimed at attenuating abnormalities in oxygen metabolism holds promise for providing novel therapeutic approaches for AD.

Circulating cardiac biomarkers, structural brain changes, and dementia: Emerging insights and perspectives

Diseases of the heart and brain are strongly linked to each other, and cardiac dysfunction is associated with cognitive decline and dementia. This link between cardiovascular disease and dementia offers opportunities for dementia prevention through prevention and treatment of cardiovascular risk factors and heart disease. Increasing evidence suggests the clinical utility of cardiac biomarkers as risk markers for structural brain changes and cognitive impairment. We propose the hypothesis that structural brain changes are the link between impaired cardiac function, as captured by blood-based cardiac biomarkers, and cognitive impairment. This review provides an overview of the literature and illustrates emerging insights into the association of markers of hemodynamic stress (natriuretic peptides) and markers of myocardial injury (cardiac troponins) with imaging findings of brain damage and cognitive impairment or dementia. Based on these findings, we discuss potential pathophysiological mechanisms underlying the association of cardiac biomarkers with structural brain changes and dementia. We suggest testable hypotheses and a research plan to close the gaps in understanding the mechanisms linking vascular damage and neurodegeneration, and to pave the way for targeted effective interventions for dementia prevention. From a clinical perspective, cardiac biomarkers open the window for early identification of patients at risk of dementia, who represent a target population for preventive interventions targeting modifiable cardiovascular risk factors to avert cognitive decline and dementia.

Association of body mass index and dietary intake with mild cognitive impairment and dementia: a retrospective cohort study

BACKGROUND

The prevalence of cognitive impairment in older adults is gradually increasing, and this is leading to many adverse outcomes. Common causes of cognitive impairment in advancing age are mild cognitive impairment (MCI) and dementia. However, how the nutritional status and nutrient intake are related to MCI and dementia is controversial. Therefore, we aimed to evaluate the association of body mass index (BMI) and dietary intake with the risk of MCI and dementia.

METHODS

This retrospective cohort study involved 821 participants aged ≥ 50 years from a previous population-based cohort study: the Electricity Generating Authority of Thailand (EGAT) study in 2013-2014 (baseline) and 2018-2019 (follow-up). Dietary intake was recorded using a 12-month self-reported food frequency questionnaire. MCI and dementia were diagnosed according to the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) criteria using the Montreal Cognitive Assessment with ADL and the Kessler Psychological Distress Scale (K10) at study entry and at the 5-year follow-up.

RESULTS

Among the 821 participants, the mean age was 60.0 ± 4.3 years, and the incidence rate of MCI and dementia was 42.5 and 11.2 per 1,000 person-years, respectively. The rate of MCI and dementia was higher in participants aged ≥ 60 years and with an education level of < 7 years. The rate of MCI was also higher in those with a BMI of ≥ 25 kg/m² and type 2 diabetes. Compared to BMI 18.5-22.9 kg/m², BMI of ≥ 25 kg/m² (odds ratio 1.91 [95% confidence interval, 1.12-3.26], p < 0.001) was associated with an increased risk of MCI after adjusted for age, education level, and type 2 diabetes. Regarding dietary intake, fresh red meat consumption was inversely associated with the risk of MCI (p = 0.037) and dementia (p = 0.011) after adjusting for age, education level, type 2 diabetes, and BMI.

CONCLUSION

Obesity was associated with a greater risk of MCI. Moreover, low consumption of fresh red meat could be a risk factor for MCI and dementia. Further studies are required to confirm and explain these findings.

The neuroprotective effects of oxygen therapy in Alzheimer’s disease: a narrative review

Alzheimer’s disease (AD) is a degenerative neurological disease that primarily affects the elderly. Drug therapy is the main strategy for AD treatment, but current treatments suffer from poor efficacy and a number of side effects. Non-drug therapy is attracting more attention and may be a better strategy for treatment of AD. Hypoxia is one of the important factors that contribute to the pathogenesis of AD. Multiple cellular processes synergistically promote hypoxia, including aging, hypertension, diabetes, hypoxia/obstructive sleep apnea, obesity, and traumatic brain injury. Increasing evidence has shown that hypoxia may affect multiple pathological aspects of AD, such as amyloid-beta metabolism, tau phosphorylation, autophagy, neuroinflammation, oxidative stress, endoplasmic reticulum stress, and mitochondrial and synaptic dysfunction. Treatments targeting hypoxia may delay or mitigate the progression of AD. Numerous studies have shown that oxygen therapy could improve the risk factors and clinical symptoms of AD. Increasing evidence also suggests that oxygen therapy may improve many pathological aspects of AD including amyloid-beta metabolism, tau phosphorylation, neuroinflammation, neuronal apoptosis, oxidative stress, neurotrophic factors, mitochondrial function, cerebral blood volume, and protein synthesis. In this review, we summarized the effects of oxygen therapy on AD pathogenesis and the mechanisms underlying these alterations. We expect that this review can benefit future clinical applications and therapy strategies on oxygen therapy for AD.

The potential of hyperbaric oxygen as a therapy for neurodegenerative diseases

The World Health Organization estimates that by the year 2040, neurodegenerative diseases will be the second leading cause of death in developed countries, overtaking cancer-related deaths and exceeded only by cardiovascular disease-related death. The search for interventions has therefore become paramount to alleviate some of this burden. Based on pathways affected in neurodegenerative diseases, hyperbaric oxygen treatment (HBOT) could be a good candidate. This therapy has been used for the past 50 years for conditions such as decompression sickness and wound healing and has been shown to have promising effects in conditions associated with neurodegeneration and functional impairments. The goal of this review was to explore the history of hyperbaric oxygen therapy, its uses, and benefits, and to evaluate its effectiveness as an intervention in treating neurodegenerative diseases. Additionally, we examined common mechanisms underlying the effects of HBOT in different neurodegenerative diseases, with a special emphasis on epigenetics.

Associations between risk of Alzheimer's disease and obstructive sleep apnea, intermittent hypoxia, and arousal responses: A pilot study

OBJECTIVES

Obstructive sleep apnea (OSA) may increase the risk of Alzheimer's disease (AD). However, potential associations among sleep-disordered breathing, hypoxia, and OSA-induced arousal responses should be investigated. This study determined differences in sleep parameters and investigated the relationship between such parameters and the risk of AD.

METHODS

Patients with suspected OSA were recruited and underwent in-lab polysomnography (PSG). Subsequently, blood samples were collected from participants. Patients' plasma levels of total tau (T-Tau) and amyloid beta-peptide 42 (Aβ42) were measured using an ultrasensitive immunomagnetic reduction assay. Next, the participants were categorized into low- and high-risk groups on the basis of the computed product (Aβ42 × T-Tau, the cutoff for AD risk). PSG parameters were analyzed and compared.

RESULTS

We included 36 patients in this study, of whom 18 and 18 were assigned to the low- and high-risk groups, respectively. The average apnea-hypopnea index (AHI), apnea, hypopnea index [during rapid eye movement (REM) and non-REM (NREM) sleep], and oxygen desaturation index (≥3%, ODI-3%) values of the high-risk group were significantly higher than those of the low-risk group. Similarly, the mean arousal index and respiratory arousal index (R-ArI) of the high-risk group were significantly higher than those of the low-risk group. Sleep-disordered breathing indices, oxygen desaturation, and arousal responses were significantly associated with an increased risk of AD. Positive associations were observed among the AHI, ODI-3%, R-ArI, and computed product.

CONCLUSIONS

Recurrent sleep-disordered breathing, intermittent hypoxia, and arousal responses, including those occurring during the NREM stage, were associated with AD risk. However, a longitudinal study should be conducted to investigate the causal relationships among these factors.

A causal association of ANKRD37 with human hippocampal volume

Human hippocampal volume has been separately associated with single nucleotide polymorphisms (SNPs), DNA methylation and gene expression, but their causal relationships remain largely unknown. Here, we aimed at identifying the causal relationships of SNPs, DNA methylation, and gene expression that are associated with hippocampal volume by integrating cross-omics analyses with genome editing, overexpression and causality inference. Based on structural neuroimaging data and blood-derived genome, transcriptome and methylome data, we prioritized a possibly causal association across multiple molecular phenotypes: rs1053218 mutation leads to cg26741686 hypermethylation, thus leads to overactivation of the associated ANKRD37 gene expression in blood, a gene involving hypoxia, which may result in the reduction of human hippocampal volume. The possibly causal relationships from rs1053218 to cg26741686 methylation to ANKRD37 expression obtained from peripheral blood were replicated in human hippocampal tissue. To confirm causality, we performed CRISPR-based genome and epigenome-editing of rs1053218 homologous alleles and cg26741686 methylation in mouse neural stem cell differentiation models, and overexpressed ANKRD37 in mouse hippocampus. These in-vitro and in-vivo experiments confirmed that rs1053218 mutation caused cg26741686 hypermethylation and ANKRD37 overexpression, and cg26741686 hypermethylation favored ANKRD37 overexpression, and ANKRD37 overexpression reduced hippocampal volume. The pairwise relationships of rs1053218 with hippocampal volume, rs1053218 with cg26741686 methylation, cg26741686 methylation with ANKRD37 expression, and ANKRD37 expression with hippocampal volume could be replicated in an independent healthy young (n = 443) dataset and observed in elderly people (n = 194), and were more significant in patients with late-onset Alzheimer's disease (n = 76). This study revealed a novel causal molecular association mechanism of ANKRD37 with human hippocampal volume, which may facilitate the design of prevention and treatment strategies for hippocampal impairment.

Neurovascular Dysfunction in Diverse Communities With Health Disparities-Contributions to Dementia and Alzheimer's Disease

Alzheimer's disease and related dementias (ADRD) are an expanding worldwide crisis. In the absence of scientific breakthroughs, the global prevalence of ADRD will continue to increase as more people are living longer. Racial or ethnic minority groups have an increased risk and incidence of ADRD and have often been neglected by the scientific research community. There is mounting evidence that vascular insults in the brain can initiate a series of biological events leading to neurodegeneration, cognitive impairment, and ADRD. We are a group of researchers interested in developing and expanding ADRD research, with an emphasis on vascular contributions to dementia, to serve our local diverse community. Toward this goal, the primary objective of this review was to investigate and better understand health disparities in Alabama and the contributions of the social determinants of health to those disparities, particularly in the context of vascular dysfunction in ADRD. Here, we explain the neurovascular dysfunction associated with Alzheimer's disease (AD) as well as the intrinsic and extrinsic risk factors contributing to dysfunction of the neurovascular unit (NVU). Next, we ascertain ethnoregional health disparities of individuals living in Alabama, as well as relevant vascular risk factors linked to AD. We also discuss current pharmaceutical and non-pharmaceutical treatment options for neurovascular dysfunction, mild cognitive impairment (MCI) and AD, including relevant studies and ongoing clinical trials. Overall, individuals in Alabama are adversely affected by social and structural determinants of health leading to health disparities, driven by rurality, ethnic minority status, and lower socioeconomic status (SES). In general, these communities have limited access to healthcare and healthy food and other amenities resulting in decreased opportunities for early diagnosis of and pharmaceutical treatments for ADRD. Although this review is focused on the current state of health disparities of ADRD patients in Alabama, future studies must include diversity of race, ethnicity, and region to best be able to treat all individuals affected by ADRD.

Shared Molecular Mechanisms among Alzheimer’s Disease, Neurovascular Unit Dysfunction and Vascular Risk Factors: A Narrative Review

Alzheimer’s disease (AD) is the most common type of dementia, affecting 24 million individuals. Clinical and epidemiological studies have found several links between vascular risk factors (VRF), neurovascular unit dysfunction (NVUd), blood-brain barrier breakdown (BBBb) and AD onset and progression in adulthood, suggesting a pathogenetic continuum between AD and vascular dementia. Shared pathways between AD, VRF, and NVUd/BBB have also been found at the molecular level, underlining the strength of this association. The present paper reviewed the literature describing commonly shared molecular pathways between adult-onset AD, VRF, and NVUd/BBBb. Current evidence suggests that VRF and NVUd/BBBb are involved in AD neurovascular and neurodegenerative pathology and share several molecular pathways. This is strongly supportive of the hypothesis that the presence of VRF can at least facilitate AD onset and progression through several mechanisms, including NVUd/BBBb. Moreover, vascular disease and several comorbidities may have a cumulative effect on VRF and worsen the clinical manifestations of AD. Early detection and correction of VRF and vascular disease by improving NVUd/BBBd could be a potential target to reduce the overall incidence and delay cognitive impairment in AD.

Identification of Potential Targets Linked to the Cardiovascular/Alzheimer’s Axis through Bioinformatics Approaches

The identification of common targets in Alzheimer’s disease (AD) and cardiovascular disease (CVD) in recent years makes the study of the CVD/AD axis a research topic of great interest. Besides aging, other links between CVD and AD have been described, suggesting the existence of common molecular mechanisms. Our study aimed to identify common targets in the CVD/AD axis. For this purpose, genomic data from calcified and healthy femoral artery samples were used to identify differentially expressed genes (DEGs), which were used to generate a protein–protein interaction network, where a module related to AD was identified. This module was enriched with the functionally closest proteins and analyzed using different centrality algorithms to determine the main targets in the CVD/AD axis. Validation was performed by proteomic and data mining analyses. The proteins identified with an important role in both pathologies were apolipoprotein E and haptoglobin as DEGs, with a fold change about +2 and −2, in calcified femoral artery vs healthy artery, respectively, and clusterin and alpha-2-macroglobulin as close interactors that matched in our proteomic analysis. However, further studies are needed to elucidate the specific role of these proteins, and to evaluate its function as biomarkers or therapeutic targets.

Anaemia and cerebrospinal fluid biomarkers of Alzheimer's pathology in cognitively normal elders: the CABLE study

Background

Anaemia has been reported to be associated with cognitive decline and Alzheimer’s disease (AD), but the associations between anaemia and cerebrospinal fluid (CSF) AD biomarkers are still unknown. This study aimed to investigate the associations between anaemia and CSF AD biomarkers.

Methods

Participants were included from the Chinese Alzheimer’s Biomarker and LifestylE (CABLE) study. The associations of anaemia and its severity with CSF AD biomarkers including β-amyloid 1–42 (Aβ42), total tau (t-tau) and phosphorylated tau (p-tau) were analysed by multiple linear regression models. Adjusted for age, gender, educational levels, APOE ε4 alleles, comorbidities (history of coronary heart disease, history of stroke, hypertension, diabetes mellitus, dyslipidaemia) and glomerular filtration rate.

Results

A total of 646 cognitively normal older adults, consisting of 117 anaemia patients and 529 non-anaemia individuals, were included in this study. Anaemia patients had lower levels of CSF Aβ42 than individuals without anaemia (p = 0.035). Besides, participants with more severe anaemia had lower CSF Aβ42 levels (p = 0.045). No significant association of anaemia with CSF t-tau and p-tau levels was found.

Conclusion

Cross-sectionally, anaemia was associated with lower CSF Aβ42 levels. These findings consolidated the causal close relationship between anaemia and AD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-021-02487-z.

Hyperoxygenation Treatment Reduces Beta-amyloid Deposition via MeCP2-dependent Upregulation of MMP-2 and MMP-9 in the Hippocampus of Tg-APP/PS1 Mice

Recently we reported that hyperoxygenation treatment reduces amyloid-beta accumulation and rescues cognitive impairment in the Tg-APP/PS1 mouse model of Alzheimer’s disease. In the present study, we continue to investigate the mechanism by which hyperoxygenation reduces amyloid-beta deposition in the brain. Hyperoxygenation treatment induces upregulation of matrix metalloproteinase-2 (MMP-2), MMP-9, and tissue plasminogen activator (tPA), the endopeptidases that can degrade amyloid-beta, in the hippocampus of Tg-APP/PS1 mice. The promoter regions of the three proteinase genes all contain potential binding sites for MeCP2 and Pea3, which are upregulated in the hippocampus after hyperoxygenation. Hyperoxygenation treatment in HT22 neuronal cells increases MeCP2 but not Pea3 expression. In HT22 cells, siRNA-mediated knockdown of Mecp2 decreases Mmp-9 expression and to a lesser extent, Mmp-2 and tPA expression. In mice, siRNA-mediated Mecp2 knockdown in the hippocampus reduces Mmp-9 expression, but not significantly Mmp-2 and tPA expression. The ChIP assay indicates that hyperoxygenation treatment in Tg-APP/PS1 mice increases MeCP2 binding to the promoter regions of Mmp-2, Mmp-9 and tPA genes in the hippocampus. Together, these results suggest that hyperoxygenation increases the expression of MMP-2, MMP-9, and tPA, of which MMP-9 is upregulated via MeCP2 in neuronal cells, and MMP-2 and tPA are upregulated through MeCP2 and other nuclear factors.

Human Cerebral Perfusion, Oxygen Consumption, and Lactate Production in Response to Hypoxic Exposure

Exposure to moderate hypoxia in humans leads to cerebral lactate production, which occurs even when the cerebral metabolic rate of oxygen (CMRO2) is unaffected. We searched for the mechanism of this lactate production by testing the hypothesis of upregulation of cerebral glycolysis mediated by hypoxic sensing. Describing the pathways counteracting brain hypoxia could help us understand brain diseases associated with hypoxia. A total of 65 subjects participated in this study: 30 subjects were exposed to poikilocapnic hypoxia, 14 were exposed to isocapnic hypoxia, and 21 were exposed to carbon monoxide (CO). Using this setup, we examined whether lactate production reacts to an overall reduction in arterial oxygen concentration or solely to reduced arterial oxygen partial pressure. We measured cerebral blood flow (CBF), CMRO2, and lactate concentrations by magnetic resonance imaging and spectroscopy. CBF increased (P < 10-4), whereas the CMRO2 remained unaffected (P > 0.076) in all groups, as expected. Lactate increased in groups inhaling hypoxic air (poikilocapnic hypoxia: $0.0136\ \frac{\mathrm{mmol}/\mathrm{L}}{\Delta{\mathrm{S}}_{\mathrm{a}}{\mathrm{O}}_2}$, P < 10-6; isocapnic hypoxia: $0.0142\ \frac{\mathrm{mmol}/\mathrm{L}}{\Delta{\mathrm{S}}_{\mathrm{a}}{\mathrm{O}}_2}$, P = 0.003) but was unaffected by CO (P = 0.36). Lactate production was not associated with reduced CMRO2. These results point toward a mechanism of lactate production by upregulation of glycolysis mediated by sensing a reduced arterial oxygen pressure. The released lactate may act as a signaling molecule engaged in vasodilation.

Anemia and the Risk of Cognitive Impairment: An Updated Systematic Review and Meta-Analysis

BACKGROUND

Cognitive impairment is one of the most common, burdensome, and costly disorders in the elderly worldwide. The magnitude of the association between anemia and overall cognitive impairment (OCI) has not been established.

OBJECTIVE

We aimed to update and expand previous evidence of the association between anemia and the risk of OCI.

METHODS

We conducted an updated systematic review and meta-analysis. We searched electronic databases, including EMBASE, PubMed, and Web of Science for published observational studies and clinical trials between 1 January 1990 and 1 June 2020. We excluded articles that were in the form of a review, letter to editors, short reports, and studies with less than 50 participants. The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines were followed. We estimated summary risk ratios (RRs) with random effects.

RESULTS

A total of 20 studies, involving 6558 OCI patients were included. Anemia was significantly associated with an increased risk of OCI (adjusted RR (aRR) 1.39 (95% CI, 1.25-1.55; p < 0.001)). In subgroup analysis, anemia was also associated with an increased risk of all-cause dementia (adjusted RR (aRR), 1.39 (95% CI, 1.23-1.56; p < 0.001)), Alzheimer's disease [aRR, 1.59 (95% CI, 1.18-2.13; p = 0.002)], and mild cognitive impairment (aRR, 1.36 (95% CI, 1.04-1.78; p = 0.02)).

CONCLUSION

This updated meta-analysis shows that patients with anemia appear to have a nearly 1.39-fold risk of developing OCI than those without anemia. The magnitude of this risk underscores the importance of improving anemia patients' health outcomes, particularly in elderly patients.

Recent development of near-infrared photoacoustic probes based on small-molecule organic dye

Photoacoustic imaging (PAI), which integrates the higher spatial resolution of optical imaging and the deeper penetration depth of ultrasound imaging, has attracted great attention. Various photoacoustic probes including inorganic and organic agents have been well fabricated in last decades. Among them, small-molecule based agents are most promising candidates for preclinical/clinical applications due to their favorite in vivo features and facile functionalization. In recent years, PAI, in the near-infrared region (NIR, 700-1700 nm) has developed rapidly and has made remarkable achievements in the biomedical field. Compared with the visible light region (400-700 nm), it can significantly reduce light scattering and meanwhile provide deeper tissue penetration. In this review, we discuss the recent developments of near-infrared photoacoustic probes based on small molecule dyes, which focus on their "always on" and "activatable" form in biomedicine. Further, we also suggest current challenges and perspectives.

A Review of the Application of Hyperbaric Oxygen Therapy in Alzheimer's Disease

Alzheimer's disease (AD) is considered as the most common cause of dementia in elderly population. While the exact mechanism of AD has not been discovered, hyperbolic oxygen therapy (HBOT) has been proven to be effective in the treatment of this degenerative disease. The objectives of this article are to review the literature available on molecular and physiological mechanisms underlying HBOT and its efficacy in treating AD and to review the effectiveness of HBOT as an alternate treatment intervention in both human and animal models. 391 full text articles were included in the review after literature search between 1980-2021 from two online data base (ScienceDirect and PubMed). The following key words were used: 'hyperbaric oxygen therapy' and 'Alzheimer disease.' Based on the outcomes of clinical and experimental studies, this review advocates the use of HBOT for the treatment of AD. This review explores future directions and recommends further research into a treatment protocol that will maintain long-term cognitive health of AD patients.

Ferulic Acid Ameliorates Alzheimer's Disease-like Pathology and Repairs Cognitive Decline by Preventing Capillary Hypofunction in APP/PS1 Mice

Brain capillaries are crucial for cognitive functions by supplying oxygen and other nutrients to and removing metabolic wastes from the brain. Recent studies have demonstrated that constriction of brain capillaries is triggered by beta-amyloid (Aβ) oligomers via endothelin-1 (ET1)-mediated action on the ET1 receptor A (ETRA), potentially exacerbating Aβ plaque deposition, the primary pathophysiology of Alzheimer's disease (AD). However, direct evidence is still lacking whether changes in brain capillaries are causally involved in the pathophysiology of AD. Using APP/PS1 mouse model of AD (AD mice) relative to age-matched negative littermates, we identified that reductions of density and diameter of hippocampal capillaries occurred from 4 to 7 months old while Aβ plaque deposition and spatial memory deficit developed at 7 months old. Notably, the injection of ET1 into the hippocampus induced early Aβ plaque deposition at 5 months old in AD mice. Conversely, treatment of ferulic acid against the ETRA to counteract the ET1-mediated vasoconstriction for 30 days prevented reductions of density and diameter of hippocampal capillaries as well as ameliorated Aβ plaque deposition and spatial memory deficit at 7 months old in AD mice. Thus, these data suggest that reductions of density and diameter of hippocampal capillaries are crucial for initiating Aβ plaque deposition and spatial memory deficit at the early stages, implicating the development of new therapies for halting or curing memory decline in AD.

SSAO/VAP-1 in Cerebrovascular Disorders: A Potential Therapeutic Target for Stroke and Alzheimer's Disease

The semicarbazide-sensitive amine oxidase (SSAO), also known as vascular adhesion protein-1 (VAP-1) or primary amine oxidase (PrAO), is a deaminating enzyme highly expressed in vessels that generates harmful products as a result of its enzymatic activity. As a multifunctional enzyme, it is also involved in inflammation through its ability to bind and promote the transmigration of circulating leukocytes into inflamed tissues. Inflammation is present in different systemic and cerebral diseases, including stroke and Alzheimer’s disease (AD). These pathologies show important affectations on cerebral vessels, together with increased SSAO levels. This review summarizes the main roles of SSAO/VAP-1 in human physiology and pathophysiology and discusses the mechanisms by which it can affect the onset and progression of both stroke and AD. As there is an evident interrelationship between stroke and AD, basically through the vascular system dysfunction, the possibility that SSAO/VAP-1 could be involved in the transition between these two pathologies is suggested. Hence, its inhibition is proposed to be an interesting therapeutical approach to the brain damage induced in these both cerebral pathologies.

Vascular Hypothesis of Alzheimer Disease: Topical Review of Mouse Models

[Figure: see text].

The impact of the 24-h movement spectrum on vascular remodeling in older men and women: a review

Aging is associated with increased risk of cardiovascular and cerebrovascular events, which are preceded by early, negative remodeling of the vasculature. Low physical activity is a well-established risk factor associated with the incidence and development of disease. However, recent physical activity literature indicates the importance of considering the 24-h movement spectrum. Therefore, the purpose of this review was to examine the impact of the 24-h movement spectrum, specifically physical activity (aerobic and resistance training), sedentary behavior, and sleep, on cardiovascular and cerebrovascular outcomes in older adults, with a focus on recent evidence (<10 yr) and sex-based considerations. The review identifies that both aerobic training and being physically active (compared with sedentary) are associated with improvements in endothelial function, arterial stiffness, and cerebrovascular function. Additionally, there is evidence of sex-based differences in endothelial function: a blunted improvement in aerobic training in postmenopausal women compared with men. While minimal research has been conducted in older adults, resistance training does not appear to influence arterial stiffness. Poor sleep quantity or quality are associated with both impaired endothelial function and increased arterial stiffness. Finally, the review highlights mechanistic pathways involved in the regulation of vascular and cerebrovascular function, specifically the balance between pro- and antiatherogenic factors, which mediate the relationship between the 24-h movement spectrum and vascular outcomes. Finally, this review proposes future research directions: examining the role of duration and intensity of training, combining aerobic and resistance training, and exploration of sex-based differences in cardiovascular and cerebrovascular outcomes.

Difluoroboron β-diketonate polylactic acid oxygen nanosensors for intracellular neuronal imaging

Critical for metabolism, oxygen plays an essential role in maintaining the structure and function of neurons. Oxygen sensing is important in common neurological disorders such as strokes, seizures, or neonatal hypoxic-ischemic injuries, which result from an imbalance between metabolic demand and oxygen supply. Phosphorescence quenching by oxygen provides a non-invasive optical method to measure oxygen levels within cells and tissues. Difluoroboron β-diketonates are a family of luminophores with high quantum yields and tunable fluorescence and phosphorescence when embedded in certain rigid matrices such as poly (lactic acid) (PLA). Boron nanoparticles (BNPs) can be fabricated from dye-PLA materials for oxygen mapping in a variety of biological milieu. These dual-emissive nanoparticles have oxygen-insensitive fluorescence, oxygen-sensitive phosphorescence, and rigid matrix all in one, enabling real-time ratiometric oxygen sensing at micron-level spatial and millisecond-level temporal resolution. In this study, BNPs are applied in mouse brain slices to investigate oxygen distributions and neuronal activity. The optical properties and physical stability of BNPs in a biologically relevant buffer were stable. Primary neuronal cultures were labeled by BNPs and the mitochondria membrane probe MitoTracker Red FM. BNPs were taken up by neuronal cell bodies, at dendrites, and at synapses, and the localization of BNPs was consistent with that of MitoTracker Red FM. The brain slices were stained with the BNPs, and the BNPs did not significantly affect the electrophysiological properties of neurons. Oxygen maps were generated in living brain slices where oxygen is found to be mostly consumed by mitochondria near synapses. Finally, the BNPs exhibited excellent response when the conditions varied from normoxic to hypoxic and when the neuronal activity was increased by increasing K+ concentration. This work demonstrates the capability of BNPs as a non-invasive tool in oxygen sensing and could provide fundamental insight into neuronal mechanisms and excitability research.

Curcumin Loaded Polymeric vs. Lipid Nanoparticles: Antioxidant Effect on Normal and Hypoxic Olfactory Ensheathing Cells

Background: Curcumin (Cur) shows anti-inflammatory and antioxidant effects on central nervous system diseases. The aim of this study was to develop Cur-loaded polymeric and lipid nanoparticles for intranasal delivery to enhance its stability and increase antioxidant effect on olfactory ensheathing cells (OECs). Methods: The nanosuspensions were subjected to physico-chemical and technological evaluation through photon correlation spectroscopy (PCS), differential scanning calorimetry (DSC) and UV-spectrophotometry. The cytotoxicity studies of nanosuspensions were carried out on OECs. A viability test was performed after 24 h of exposure of OECs to unloaded and curcumin-loaded nanosuspensions. The potential protective effect of Cur was assessed on hypoxic OECs cells. Uptake studies were performed on the same cell cultures. Thermal analysis was performed to evaluate potential interaction of Cur with a 1,2-Dimyristoyl-sn-glycero-3-phosphocholine (DMPC) biomembrane model. Results: PCS analysis indicated that lipid and polymeric nanosuspensions showed a mean size of 127.10 and 338.20 nm, respectively, high homogeneity and negative zeta potential. Incorporation of Cur into both nanocarriers increased drug stability up to 135 days in cryoprotected freeze-dried nanosuspensions. Cell viability was improved when hypoxic OECs were treated with Cur-loaded polymeric and lipid nanosuspensions compared with the control. Conclusions: Both nanocarriers could improve the stability of Cur as demonstrated by technological studies. Biological studies revealed that both nanocarriers could be used to deliver Cur by intranasal administration for brain targeting.

Red Cell Distribution Width and Dementia Among Rural-Dwelling Older Adults: The MIND-China Study

BACKGROUND

Evidence has emerged that anemia is associated with dementia, but data on the relationships of red blood cell distribution width (RDW) with dementia and cognitive function in older adults are sparse.

OBJECTIVE

We sought to investigate the associations of RDW with dementia and global cognitive performance among rural-dwelling Chinese older adults and further to examine their associations by anemia status.

METHODS

This population-based cross-sectional study included 5,115 participants (age≥65 years, 57.0%women) in the baseline examination (March-September 2018) of the Multimodal Interventions to Delay Dementia and Disability in rural China (MIND-CHINA). We collected data through face-to-face interviews, clinical examinations, and laboratory tests. Global cognitive function was evaluated using the Mini-Mental State Examination (MMSE). We defined dementia, Alzheimer's disease (AD), and vascular dementia (VaD) following the respective international criteria. Data were analyzed using multinomial logistic and general linear regression models.

RESULTS

Of all participants, 300 were diagnosed with dementia, including 195 with AD and 95 VaD. The multiple-adjusted odds ratio of dementia associated with quartiles of RDW were 1.45 (95%CI: 0.87-2.44), 1.00 (reference), 1.77 (1.07-2.93), and 2.28 (1.40-3.72). Similar J-shaped patterns existed for the association of RDW with odds ratio of AD and VaD. Anemia was not significantly associated with dementia. The J-shaped associations of RDW with dementia and subtypes were statistically evident only among participants without anemia. There was an inverted J-shaped relationship between RDW quartiles and β-coefficients of MMSE score.

CONCLUSION

There is a J-shaped association between RDW level and likelihood of dementias among rural-dwelling Chinese older adults, especially among people without anemia.

Liver-Brain Axis in Sporadic Alzheimer's Disease: Role of Ten Signature Genes in a Mouse model

AIM

Poor nutritional effect of junk food induces injurious adversities to the liver and brain but still most of the developing nations survives on these diets to compensate for fast-paced lifestyle. Aim of the study is to infer the proteinconnections behind liver-brain axis and identify the role of these proteins in causing neurodegenerative disorders.

BACKGROUND

Chronic consumption of fructose and fat rich food works as a toxin in body and have the ability to cause negative metabolic shift. Recently a study was published in Annals of Internal Medicine (2019) citing the loss of vision and hearing in a 14-year-old boy whose diet was strictly restricted to fries and junk-food for almost a decade. This puts the entire body on insulin resistance and related co-morbidities and causes simultaneous damaging effects in liver as well brain. This work provides insights into liver-brain axis and explains how liver is involved in brain related disorders.

OBJECTIVE

In this study transcriptomic data relating to chronic eating of junk-food was analyzed and simultaneous damage that happens in liver and brain was assessed at molecular level.

METHOD

Transcriptomic study was taken from GEO database and analysed to find out the genes dysregulated in both liver and brain during this metabolic stress. Cytoscapev3.7 was used to decipher the signalling between liver and brain. This connection between both was called as Liver-Brain axis.

RESULT

The results obtained from our study indicates the role of TUBB5-HYOU1-SDF2L1-DECR1-CDH1-EGFR-SKP2- SOD1-IRAK1-FOXO1 gene signature towards the decline of concurrent liver and brain health. Dysregulated levels of these genes are linked to molecular processes like cellular senescence, hypoxia, glutathione synthesis, amino acid modification, increased nitrogen content, synthesis of BCAAs, cholesterol biosynthesis, steroid hormone signalling and VEGF pathway.

CONCLUSION

We strongly advocate that prolonged consumption of junk food is a major culprit in brain related disorders like Alzheimer's disease and propose that receptors for brain diseases lie outside the brain and aiming them for drug discovery and design may be beneficial in future clinical studies. This study also discusses the connection between NAFLD (nonalcoholic fatty liver disease) and sAD (sporadic Alzheimer's disease) owing to liver-brain axis.

The gut microbiome as a target for adjuvant therapy in obstructive sleep apnea

Introduction: Gut dysbiosis is assumed to play a role in obstructive sleep apnea (OSA)-associated morbidities. Pre- and probiotics, short chain fatty acids (SCFA) and fecal matter transplantation (FMT) may offer potential as novel therapeutic strategies that target this gut dysbiosis. As more mechanisms of OSA-induced dysbiosis are being elucidated, these novel approaches are being tested in preclinical and clinical development. Areas covered: We examined the evidence linking OSA to gut dysbiosis and discuss the effects of pre- and probiotics on associated cardiometabolic, neurobehavioral and gastrointestinal disorders. The therapeutic potential of SCFA and FMT are also discussed. We reviewed the National Center for Biotechnology Information database, including PubMed and PubMed Central between 2000 - 2020. Expert opinion: To date, there are no clinical trials and only limited evidence from animal studies describing the beneficial effects of pre- and probiotic supplementation on OSA-mediated dysbiosis. Thus, more work is necessary to assess whether prebiotics, probiotics and SCFA are promising future novel strategies for targeting OSA-mediated dysbiosis.

Genome-wide identification of novel long non-coding RNAs and their possible roles in hypoxic zebrafish brain

Long non-coding RNAs (lncRNAs) are the master regulators of numerous biological processes. Hypoxia causes oxidative stress with severe and detrimental effects on brain function and acts as a critical initiating factor in the pathogenesis of Alzheimer's disease (AD). From the RNA-Seq in the forebrain (Fb), midbrain (Mb), and hindbrain (Hb) regions of hypoxic and normoxic zebrafish, we identified novel lncRNAs, whose potential cis targets showed involvement in neuronal development and differentiation pathways. Under hypoxia, several lncRNAs and mRNAs were differentially expressed. Co-expression studies indicated that the Fb and Hb regions' potential lncRNA target genes were involved in the AD pathogenesis. In contrast, those in Mb (cry1b, per1a, cipca) was responsible for regulating circadian rhythm. We identified specific lncRNAs present in the syntenic regions between zebrafish and humans, possibly functionally conserved. We thus identified several conserved lncRNAs as the probable regulators of AD genes (adrb3b, cav1, stat3, bace2, apoeb, psen1, s100b).

The Impact of Low Hemoglobin Levels on Cognitive Brain Functions

The prevalence of dementia is around 5% worldwide in people above 65 years, which increases with aging. Alzheimer's disease is the most common cause of dementia in the elderly. On the other hand, anemia is considered one of the most prevalent comorbidities in the elderly with a prevalence of 11% in those above the age of 65. It is crucial that we find the association between anemia and dementia, as this linkage can prove beneficial. Many currently conducted studies support the idea that anemia is a significant risk factor for dementia. However, some studies still consider anemia and dementia as just an aging process, nothing more. In our study, we found that there are a lot of theories, such as low brain hemoglobin associated with low oxygen levels, which leads to neuron damage. One article mentioned that it is dependent on the level of hemoglobin as an effect with mild to moderate anemia, but apparent with severe forms of it. Researchers are expected to further explore and identify the exact relationship between anemia and dementia. We used the PubMed database as the principal source for data search and extracted articles exploring the relationship and role of anemia in decreasing the cognitive brain functions in the elderly. We reviewed 35 different articles, including clinical trials, review papers, randomized controlled trials (RCTs), and original research published between 2010 and 2020 to find commonly accepted pathophysiology that highlights how anemia causes a decrease in cognitive brain functions.

Potential Drug Candidates to Treat TRPC6 Channel Deficiencies in the Pathophysiology of Alzheimer's Disease and Brain Ischemia

Alzheimer’s disease and cerebral ischemia are among the many causative neurodegenerative diseases that lead to disabilities in the middle-aged and elderly population. There are no effective disease-preventing therapies for these pathologies. Recent in vitro and in vivo studies have revealed the TRPC6 channel to be a promising molecular target for the development of neuroprotective agents. TRPC6 channel is a non-selective cation plasma membrane channel that is permeable to Ca²⁺. Its Ca²⁺-dependent pharmacological effect is associated with the stabilization and protection of excitatory synapses. Downregulation as well as upregulation of TRPC6 channel functions have been observed in Alzheimer’s disease and brain ischemia models. Thus, in order to protect neurons from Alzheimer’s disease and cerebral ischemia, proper TRPC6 channels modulators have to be used. TRPC6 channels modulators are an emerging research field. New chemical structures modulating the activity of TRPC6 channels are being currently discovered. The recent publication of the cryo-EM structure of TRPC6 channels should speed up the discovery process even more. This review summarizes the currently available information about potential drug candidates that may be used as basic structures to develop selective, highly potent TRPC6 channel modulators to treat neurodegenerative disorders, such as Alzheimer’s disease and cerebral ischemia.

The silence of the fats: A MAM's story about Alzheimer

The discovery of contact sites was a breakthrough in cell biology. We have learned that an organelle cannot function in isolation, and that many cellular functions depend on communication between two or more organelles. One such contact site results from the close apposition of the endoplasmic reticulum (ER) and mitochondria, known as mitochondria-associated ER membranes (MAMs). These intracellular lipid rafts serve as hubs for the regulation of cellular lipid and calcium homeostasis, and a growing body of evidence indicates that MAM domains modulate cellular function in both health and disease. Indeed, MAM dysfunction has been described as a key event in Alzheimer disease (AD) pathogenesis. Our most recent work shows that, by means of its affinity for cholesterol, APP-C99 accumulates in MAM domains of the ER and induces the uptake of extracellular cholesterol as well as its trafficking from the plasma membrane to the ER. As a result, MAM functionality becomes chronically upregulated while undergoing continual turnover. The goal of this review is to discuss the consequences of C99 elevation in AD, specifically the upregulation of cholesterol trafficking and MAM activity, which abrogate cellular lipid homeostasis and disrupt the lipid composition of cellular membranes. Overall, we present a novel framework for AD pathogenesis that can be linked to the many complex alterations that occur during disease progression, and that may open a door to new therapeutic strategies.

Molecular and Therapeutic Aspects of Hyperbaric Oxygen Therapy in Neurological Conditions

In hyperbaric oxygen therapy (HBOT), the subject is placed in a chamber containing 100% oxygen gas at a pressure of more than one atmosphere absolute. This treatment is used to hasten tissue recovery and improve its physiological aspects, by providing an increased supply of oxygen to the damaged tissue. In this review, we discuss the consequences of hypoxia, as well as the molecular and physiological processes that occur in subjects exposed to HBOT. We discuss the efficacy of HBOT in treating neurological conditions and neurodevelopmental disorders in both humans and animal models. We summarize by discussing the challenges in this field, and explore future directions that will allow the scientific community to better understand the molecular aspects and applications of HBOT for a wide variety of neurological conditions.

MAM and C99, key players in the pathogenesis of Alzheimer's disease

Inter-organelle communication is a rapidly-expanding field that has transformed our understanding of cell biology and pathology. Organelle-organelle contact sites can generate transient functional domains that act as enzymatic hubs involved in the regulation of cellular metabolism and intracellular signaling. One of these hubs is located in areas of the endoplasmic reticulum (ER) connected to mitochondria, called mitochondria-associated ER membranes (MAM). These MAM are transient lipid rafts intimately involved in cholesterol and phospholipid metabolism, calcium homeostasis, and mitochondrial function and dynamics. In addition, γ-secretase-mediated proteolysis of the amyloid precursor protein 99-aa C-terminal fragment (C99) to form amyloid β also occurs at the MAM. Our most recent data indicates that in Alzheimer's disease, increases in uncleaved C99 levels at the MAM provoke the upregulation of MAM-resident functions, resulting in the loss of lipid homeostasis, and mitochondrial dysfunction. Here, we discuss the relevance of these findings in the field, and the contribution of C99 and MAM dysfunction to Alzheimer's disease neuropathology.

Oxygen-Dependent Accumulation of Purine DNA Lesions in Cockayne Syndrome Cells

Cockayne Syndrome (CS) is an autosomal recessive neurodegenerative premature aging disorder associated with defects in nucleotide excision repair (NER). Cells from CS patients, with mutations in CSA or CSB genes, present elevated levels of reactive oxygen species (ROS) and are defective in the repair of a variety of oxidatively generated DNA lesions. In this study, six purine lesions were ascertained in wild type (wt) CSA, defective CSA, wtCSB and defective CSB-transformed fibroblasts under different oxygen tensions (hyperoxic 21%, physioxic 5% and hypoxic 1%). In particular, the four 5′,8-cyclopurine (cPu) and the two 8-oxo-purine (8-oxo-Pu) lesions were accurately quantified by LC-MS/MS analysis using isotopomeric internal standards after an enzymatic digestion procedure. cPu levels were found comparable to 8-oxo-Pu in all cases (3–6 lesions/10⁶ nucleotides), slightly increasing on going from hyperoxia to physioxia to hypoxia. Moreover, higher levels of four cPu were observed under hypoxia in both CSA and CSB-defective cells as compared to normal counterparts, along with a significant enhancement of 8-oxo-Pu. These findings revealed that exposure to different oxygen tensions induced oxidative DNA damage in CS cells, repairable by NER or base excision repair (BER) pathways. In NER-defective CS patients, these results support the hypothesis that the clinical neurological features might be connected to the accumulation of cPu. Moreover, the elimination of dysfunctional mitochondria in CS cells is associated with a reduction in the oxidative DNA damage.

Crocin Treatment after Maternal Hypoxia Attenuates Spatial Memory Impairment and Expression of BACE1 and HIF-1α in Rat Offspring Brain

Introduction

Hypoxia via expression of Hypoxia-Inducible Factor-1 (HIF-1) is an important and effective factor in the onset and progression of memory disorders, such as Alzheimer Disease (AD). The activity of β-secretase (BACE1) is increased in hypoxia conditions. BACE1 triggers a cascade of pathological events resulting in AD. Crocin acts as a memoryimproving agent but its molecular mechanism is not well-known. Therefore, in this study, the effect of crocin on spatial memory, HIF-1α, and BACE1 gene expression was investigated in rat offspring under maternal hypoxia.

Methods

Female pregnant rats on the 20th day of pregnancy were divided into 4 groups, including sham, crocin-treated, hypoxia, and hypoxia group treated with crocin. In the hypoxia groups, pregnant rats were exposed to 7% oxygen and 93% nitrogen intensity for 3 h. In the crocin-treated group, crocin (30 mg/kg) was injected at P14-28 (i.p). At the end, Morris water maze was used to assess spatial memory and real-time polymerase chain reaction was performed to measure the expression of BACE1 and HIF-1α genes in the brain of offspring.

Results

Maternal hypoxia impaired memory compared with the sham group. However, crocin treatment improved cognitive behavior. HIF-1α and BACE1 expressions were upregulated in the brain of offspring in the hypoxia group. Crocin treatment could attenuate the expression of both genes.

Conclusion

According to our results, down-regulation of HIF-1α and BACE1 gene expressions in the brain of rat offspring after crocin treatment can be suggested as a molecular mechanism for crocin to improve spatial memory.

Anemia and incidence of dementia in patients with new-onset type 2 diabetes: a nationwide population-based cohort study

INTRODUCTION

This study aimed to examine the association between anemia and the incidence of dementia in patients with new-onset type 2 diabetes.

RESEARCH DESIGN AND METHODS

This study used the Korean National Health Insurance Service-Health Screening Cohort and included 32 590 participants aged ≥40 years who were diagnosed with new-onset type 2 diabetes between 2004 and 2007 and followed up until 2013. Anemia was defined according to the criteria provided by the WHO, hemoglobin <120 g/L for women and <130 g/L for men, and was measured from after diagnosis date of type 2 diabetes to 2007. Dementia was defined by the Classification of Diseases 10th revision code as primary diagnosis and was measured from after hemoglobin measurement to 2013. We calculated the adjusted HR (AHR) and 95% CI to assess the risk of dementia using multivariable Cox proportional hazards regression models.

RESULTS

We identified 1682 patients who developed dementia within a 7.5-year follow-up. Among patients with type 2 diabetes, patients with anemia were associated with an increased risk of dementia than those without anemia (AHR, 1.21; 95% CI 1.06 to 1.39). Patients with mild (AHR, 1.18; 95% CI 1.03 to 1.38) and moderate (AHR, 1.39; 95% CI 1.06 to 1.83) anemia were associated with an increased risk of dementia than those without anemia among patients with type 2 diabetes. Men (AHR, 1.47; 95% CI 1.16 to 1.83) and middle-aged adults (AHR, 1.31; 95% CI 1.03 to 1.75) with anemia were associated with an increased risk of dementia than their counterparts without anemia among patients with type 2 diabetes.

CONCLUSIONS

Our findings suggest that anemia is significantly associated with an increased risk of dementia among patients with newly diagnosed type 2 diabetes.

Protective effect of nitronyl nitroxide against hypoxia-induced damage in PC12 cells

Hypoxia induces cellular oxidative stress that is associated with neurodegenerative diseases. HPN (4'-hydroxyl-2-substituted phenyl nitronyl nitroxide), a stable nitronyl nitroxide, has excellent free radical scavenging properties. The purpose of this study was to investigate the protective effects of HPN on hypoxia-induced damage in PC12 cells. It was shown that HPN significantly attenuated hypoxia-induced loss of cell viability, release of lactate dehydrogenase (LDH), and morphological changes in PC12 cells. Moreover, hypoxic PC12 cells had increased levels of reactive oxygen species (ROS), malondialdehyde (MDA), and expression of HIF-1α and VEGF, but had reduced levels of superoxide dismutase (SOD) and catalase (CAT), and HPN reversed these changes. HPN also inhibited hypoxia-induced cell apoptosis via suppressing the expression of Bax, cytochrome c, and caspase-3, and inducing the expression of Bcl-2. These results indicate that the protective effects of HPN on hypoxia-induced damage in PC12 cells is associated with the suppression of hypoxia-induced oxidative stress and cell apoptosis. HPN could be a promising candidate for the development of a novel neuroprotective agent.

Potential Indirect Mechanisms of Cognitive Enhancement After Long-Term Resistance Training in Older Adults

The prevalence of dementia and other age-associated cognitive disorders is steadily increasing worldwide. With no cure after diagnosis, successful treatment likely requires maximum adherence to preventative countermeasures. Many potential risk factors are modifiable through exercise. Specifically, mounting evidence suggests that long-term resistance training (RT) can help maintain cognitive abilities with aging and have additional benefits to overall brain health. Physical therapists are uniquely positioned to administer such clinical interventions designed to slow disease progression. However, a neuroscientific foundation for these benefits must be established to justify the integration of RT for brain health into practice. The mechanisms of cognitive decline are commonly linked to fundamental processes of aging. Even healthy older adults experience decreases in physical capacity, vascular function, brain structure and function, glucose regulation, inflammation, mood, and sleep quality. Yet, clinical trials involving RT in older adults have consistently demonstrated improvements in each of these systems with concomitant enhancement of cognitive performance. Beneficial adaptations may indirectly or directly mediate benefits to brain function, and understanding this relationship can help us develop optimal intervention strategies for the aging population.

Hemoglobin, anemia, and poststroke cognitive impairment: A cohort study

OBJECTIVES

Several studies have demonstrated that anemia was associated with cognitive impairment. The aim of this study was to explore the relationship between hemoglobin and cognitive impairment in patient with acute ischemic stroke.

METHODS

In total, 326 patients with acute ischemic stroke were followed up for 1 month. The main outcome was the incidence and severity of poststroke cognitive impairment (PSCI) assessed by Mini-Mental State Examination (MMSE). The impact of hemoglobin levels and anemia on PSCI was assessed by multiple regression models controlling for potential confounders.

RESULTS

During the 1-month follow-up, 193 (59.2%) patients developed PSCI. Anemia was independently associated with PSCI (OR = 3.637; 95% CI, 1.216-10.881; P = .021) after adjusting for demographics, vascular risk factors, stroke severity, and functional outcome. When the hemoglobin levels stratified into tertiles, higher hemoglobin levels were associated with better cognitive function. This result was however not significant after adjusting for the same confounders above.

CONCLUSIONS

Low hemoglobin levels are associated with an increased risk of PSCI. Targeted interventions in this population may reduce the incidence of PSCI and require further evaluation.

Response of neuroglia to hypoxia-induced oxidative stress using enzymatically crosslinked hydrogels

Three-dimensional cultures have exciting potential to mimic aspects of healthy and diseased brain tissue to examine the role of physiological conditions on neural biomarkers, as well as disease onset and progression. Hypoxia is associated with oxidative stress, mitochondrial damage, and inflammation, key processes potentially involved in Alzheimer's and multiple sclerosis. We describe the use of an enzymatically-crosslinkable gelatin hydrogel system within a microfluidic device to explore the effects of hypoxia-induced oxidative stress on rat neuroglia, human astrocyte reactivity, and myelin production. This versatile platform offers new possibilities for drug discovery and modeling disease progression.

Effects of chronic hypoxia on the expression of seladin-1/Tuj1 and the number of dark neurons of hippocampus

BACKGROUND

There are evidences showing the relation between chronic hypoxia and Alzheimer's disease (AD) as a metabolic neurodegenerative disease. This study was designed to evaluate the effects of chronic hypoxia on factors which characterized in AD to introduce a new model of AD-dementia.

METHODS AND MATERIALS

Twenty-four male rats were randomly divided in three groups: Control group (Co), Sham group (Sh), Hypoxia induction group (Hx, exposed to hypoxic chamber [oxygen 8% and nitrogen 92%] for 30 days, 4 h/day). Spatial learning and memory were analyzed using the Morris water maze task. At day 30 after hypoxia period, animals were sacrificed and serum was gathered for pro-inflammatory cytokines (interleukin-1β and tumor necrosis factor) measurements and brains were used for molecular and histopathological investigations.

RESULTS

According to behavioral studies, a significant impairment was seen in Hx group (P < 0.05). TNF-α and IL-1β showed a significant enhanced in Hx group comparing with Co group and Sh group (P < 0.05). As well, the gene expression of seladin-1, Tuj1 and the number of seladin-1+, Tuj1+neurons significantly decreased and also the mean number of dark neurons significantly increased in CA1 and CA3 regions of hippocampus.

CONCLUSIONS

In this study, a new model of AD was developed which showed the underlying mechanisms of AD and its relations with chronic hypoxia. Hypoxia for 30 days decreased seladin-1, Tuj1 expression, increased the number of dark neurons, and also induced memory impairment. These results indicated that chronic hypoxia mediated the dementia underlying AD and AD-related pathogenesis in rat.

Post-operative delirium associated with metabolic alterations following hemi-arthroplasty in older patients

BACKGROUND

post-operative delirium (POD) is a common complication in older patients, though a possible link between metabolic changes and POD development has yet to be investigated.

METHODS

older patients with hip fracture who underwent hemi-arthroplasty were recruited, and delirious states were assessed for 3 days after surgery using the confusion assessment method-Chinese revision. Simultaneously, fasting blood samples were collected on the morning of surgery and on the first post-operative day. Ultimately, 244 older patients who met the inclusion and exclusion criteria were assessed. Blood samples from 60 patients with POD and 60 matched controls were analysed using metabolomics platforms.

RESULTS

sixty patients (24.6%) developed POD. Principal component analysis scores plot and cross-validated scores plots from orthogonal partial least squares-discriminant analysis were implemented to visualise the differences in metabolites between the two groups before and after surgery (P < 0.05). Our data indicate that levels of ω3 and ω6 fatty acids were lower in the POD group than in the NPOD (non-POD) group both before and after surgery; tricarboxylic cycle intermediate levels were lower in the POD group than in the NPOD group, but glycolysis products were higher in the POD group than in the NPOD group after surgery. Furthermore, the branched-chain amino acid (BCAA)/aromatic amino acid ratio was lower in the POD group than in the NPOD group after surgery.

CONCLUSIONS

metabolic abnormalities, including deficiencies in ω3 and ω6 fatty acids, perturbations in tricarboxylic cycle and oxidative stress and metabolic imbalances in BCAA and AAA might contribute to POD development.

Voluntary exercise increases brain tissue oxygenation and spatially homogenizes oxygen delivery in a mouse model of Alzheimer's disease

Although vascular contributions to dementia and Alzheimer's disease (AD) are increasingly recognized, the potential brain oxygenation disruption associated with AD and whether preventive strategies to maintain tissue oxygenation are beneficial remain largely unknown. This study aimed to examine (1) whether brain oxygenation is compromised by the onset of AD and (2) how voluntary exercise modulates the influence of AD on brain oxygenation. In vivo 2-photon phosphorescence lifetime microscopy was used to investigate local changes of brain tissue oxygenation with the progression of AD and its modulation by exercise in the barrel cortex of awake transgenic AD mice. Our results show that cerebral tissue oxygen partial pressure (PO₂) decreased with the onset of AD. Reduced PO₂ was associated with the presence of small near-hypoxic areas, an increased oxygen extraction fraction, and reduced blood flow, observations that were all reverted by exercise. AD and age also increased the spatial heterogeneity of brain tissue oxygenation, which was normalized by exercise. Ex vivo staining also showed fewer amyloid-β (Aβ) deposits in the exercise group. Finally, we observed correlations between voluntary running distance and cerebral tissue oxygenation/blood flow, suggesting a dose-response relationship of exercise on the brain. Overall, this study suggests that compromised brain oxygenation is an indicator of the onset of AD, with the emergence of potential deleterious mechanisms associated with hypoxia. Furthermore, voluntary exercise enhanced the neurovascular oxygenation process, potentially offering a means to delay these changes.

Traumatic brain injury triggers APP and Tau cleavage by delta-secretase, mediating Alzheimer's disease pathology

Traumatic brain injury (TBI) is associated in some studies with clinical dementia, and neuropathological features, including amyloid plaque deposition and Tau neurofibrillary degeneration commonly identified in Alzheimer's disease (AD). However, the molecular mechanisms linking TBI to AD remain unclear. Here we show that TBI activates transcription factor CCAAT/Enhancer Binding Protein Beta (C/EBPβ), increasing delta-secretase (AEP) expression. Activated AEP cleaves both APP and Tau at APP N585 and Tau N368 sites, respectively, which mediate AD pathogenesis by promoting Aβ production and Tau hyperphosphorylation and inducing neuroinflammation and neurotoxicity. Knockout of AEP or C/EBPβ diminishes TBI-induced AD-like pathology and cognitive impairment in the 3xTg AD mouse model. Remarkably, viral expression of AEP-resistant Tau N368A in the hippocampus of 3xTg mice also ameliorates the pathological and cognitive consequences of TBI. Finally, clinical TBI activates C/EBPβ and escalates AEP expression, leading to APP N585 and Tau N368 proteolytic cleavage in TBI patient brains. Hence, our findings support a potential role for AEP in linking TBI exposure with AD pathogenesis.